In some fluid ejection devices, such as printheads, a drop ejecting element is formed on a substrate and fluid is routed to an ejection chamber of the drop ejecting element through an opening or slot in the substrate. Often, the substrate is a silicon wafer and the slot is formed in the wafer by chemical etching. Existing chemical etching processes, however, result in etch angles that cause a very wide backside opening of the slot in the substrate. The backside of the substrate is defined as a side of the substrate opposite of which the drop ejecting element is formed.
Unfortunately, the wide backside slot opening limits how close to each other slots can be formed in a particular die. In addition, the wide backside slot opening reduces useful area of the backside of the substrate. For example, the wide backside slot opening reduces adhesion area of the backside of the substrate.
Accordingly, it is desired to minimize a size of the opening in the backside of the substrate.